If the path does not contain any spaces, then you can omit the quotes and the '&' operator

PS C:\> C:\Belfry\Myscript.ps1

If the script is in the current directory, you must indicate this using .\ (or ./ will also work)

PS C:\> .\Myscript.ps1

When you invoke a script using the syntax above, variables and functions defined in the script will disappear when the script ends.1

Dot Sourcing

When you dot sourcea script, all variables and functions defined in the script will persist even when the script ends.

Run a script by dot-sourcing it:

PS C:\> . "C:\Belfry\My first Script.ps1"

Dot-sourcing a script in the current directory:

PS C:\> . .\Myscript.ps1"

Run a CMD batch file

Run a batch script from PowerShell: PS C:\> ./demo.cmd

If the batch
script contains any internal commands then it must be run by calling the CMD.exe shell and passing the batch file: PS C:\> C:\windows\system32\cmd /c c:\batch\demo.cmd
Note, this works for .cmd but not .bat files.

Run a VBScript file

Run a vb script from PowerShell: PS C:\> cscript c:\batch\demo.vbs

The System Path

If you run a script (or even just enter a command) without specifying the fully qualified path name, PowerShell will search for it as follows:
Firstly it will look at currently defined aliases, then currently defined functions and lastly commands located in the system path.

1unless they are explicitly defined as globals: Function SCOPE:GLOBAL or Filter SCOPE:GLOBAL or Set-Variable -scope "Global"

# Yeah - I'm gonna run to you, cause when the feelins right I'm gonna stay all night, I'm gonna run to you# ~ Bryan Adams